Is the a way of taking a curve that is projected onto a topographic surface, extrude it up to a flat top. Basically I have the out line of some 20000 houses I want to extrude and put on a topographic map. So I have the outline of the houses projected already and I want to go up so the roof is flat (opposed to being the shape of the original curve.

Alternatively is there a command that can flatten a curve on its current plane (opposed to flattening on cplane).